How long should the radial artery be compressed during the Allen test?

The Allen test is performed to assess the patency of the ulnar artery and is commonly used prior to procedures such as arterial blood gas sampling from the radial artery. During the test, both the radial and ulnar arteries are compressed. The purpose of compressing the radial artery for a specific duration is to observe how quickly blood flow returns to the hand when the radial artery is released, indicating that the ulnar artery has sufficient blood supply to compensate for any region supplied by the radial artery.

Compressing the radial artery for one minute allows adequate time for the palm to become ischemic, and then the release of pressure will show the return of color to the hand. This duration is sufficiently long to evaluate the collateral circulation provided by the ulnar artery without causing prolonged ischemic effects. While shorter or longer durations may not accurately evaluate arterial patency, one minute provides a standard and practical timeframe for reliable results.